The present invention generally relates to a method for providing a semiconductor device including contact studs for contacting a semiconductor substrate, said contact studs being embedded in an insulating structure. The present invention also relates to a corresponding semiconductor device.
Hereinbelow, the technical term semiconductor substrate is used in a general sense, i.e. said substrate may be a wafer substrate, a wafer substrate carrying an integrated circuit, a multi-wafer substrate and so on.
FIGS. 1 and 2 are schematic illustrations of process steps of a known method for providing a semiconductor device including contact studs for contacting a semiconductor substrate, said contact studs being embedded in an insulating structure.
In FIG. 1, reference sign 10 denotes a semiconductor substrate carrying an integrated circuit, which is not shown in detail here. Although not limited thereto, in this example, the semiconductor substrate 10 is a silicon substrate. Reference sign 20 denotes an oxide layer having holes, wherein contact studs are to be formed. To form said contact studs, in a first step a liner layer 30 made of titanium is deposited in a conformal deposition process. In a second step, on said liner layer 30 a metal layer 40 made of tungsten is deposited such that it covers the whole structure which results in the status shown in FIG. 1.
As may be seen from FIG. 2, in a third step a metal polish is performed by a chemical-mechanical polishing step CMP1 in order to remove the tungsten layer 40 and the titanium layer 30 from the upper surface of the insulating oxide layer 20 such that said contact studs 100 are formed. During said metal polishing, the upper surface of said oxide layer 20 incurs micro-scratching effects leaving micro-scratches 60 on said upper surface. Moreover, liner residuals 50 may be left on said upper surface and/or in said micro-scratches 60 of said oxide layer 20. In addition, if the metal polishing step is performed too long, the contact studs can protrude too far up and cause metal openings on subsequent layers, as indicated in FIG. 2. Also, there may be a loss or distortion of oxide defined features such as overlay and alignment marks.
The liner residuals 50 and the subsequently performed metal position in the micro-scratches 60 can cause shorts when they go untreated. In addition, there can also be an area where residuals 50 from subsequent processing steps, either wet or dry, can be a source of additional defects or contamination.
The present invention seeks to provide a method for providing a semiconductor device including contact studs for contacting a semiconductor substrate, said contact studs being embedded in an insulating structure, which mitigate or avoid these and other disadvantages and limitations of the prior art.